Incandescent body for electric lamps.



ANTON LEDERER, OF VIENNA, AUSTRIA-HUNGARY.

INCANDESCEN'I. BODY FOR ELECTRIC LAMPS.

Specification of Letters Patent.

Patented Apr. 18, 1916.

Application filed December 20, 1906. Serial No. 348,734.

To all whom it may concern:

Be it known that I, ANTON LEDERER, a

subject of the Emperor of Austria-Hungary,

essentially composed of metals that tend to alter internally under theinfluence of electric currents and to the process of manufacturing thesame.

It consists generally in the production of more durable and eflicientincandescent filaments, containing an intimate mixture of such a metalwith another metal or metallic compound which causes the filaments toresist internal alterations during their use.

In the manufacture of filaments for incandescent lamps, and especiallyof filaments consisting of pure tungsten metal, it has been observedthat, after burning for some time, an alteration in the structure ofsuch filaments takes place. This alteration, which manifests itself in adisplace- .ment of sections of a filament with respect to its lonitudinal axis, is usually designated by t e terms off-setting orfaulting, and is probably due to the crystallization of the metal.The'appearance of this crystalline structure has the deleterious effeetthat it renders the filaments considerably more brittle than they werebefore and it thus increases very greatly the liability of the filamentsbreaking when the lamp is in service or is subjected to shocks. I havediscovered that by the addition of small percentages of suitablesubstances to the tungsten this crystallization and consequentdeterioration of the filament can be largely obviated or entirelyprevented. In one of the ordinary processes of manufacturing tungstenfilaments it is usual to bring the tungsten metal, or an appropriatetungsten compound, into the shape of a plastic paste by means of anaddition of a suitable binding material. I have found that when a smallamount of oxygen or oxygen containing compounds of rare earth metals andlike materials, such as thorium, zirconium, erbium, cerium, lanthanum,etc., is added to a paste of such a character, or to the materials usedin maln'ng metallic filaments according to other processes, theresulting filament is structurally different from a filament consistingonly of tungsten and that thechangeover of the filament into thecrystalline structure is considerably delayed or altogether prevented.The presence of a bind- 1ng material, is, of course, immaterial, nordoes it matter at what time durin the process of manufacturing theseadditions are made to the tungsten metal or tungsten compound, as longas they produce the desired result in the finished filament.

In order not to affect the efliciency of the filament or todeleteriously affect its mechanical qualities, it is necessary that thequantities of the above substances, which are to be added to thetungsten, be comparatively small, so that, after the finished filamentis obtained, the tungsten is the largely predominating element in it.

Only such combinations of the auxiliary ingredients should be added tothe tungsten as'will have no harmful efiect on the original constituentsof the filament or on the resultant filamentary material. Especiallysuitable for the purpose are oxygen containing compounds of the rareearth metals, such as the nitrates, ammonium nitrates, oxalates,citrates, tartrates, etc., as these can be easily and expeditiouslyincorporated with the tungsten paste. The quantities of such additionsshould be such that the tungsten element of the resultant filament stilllargely predominates, but within this range the quantity may be variedwithin reasonable limits. Thus, for instance, I have found thatsatisfactory results are obtained by adding to the ordinary tungstenpaste a quantity of thorium oxid up to about 740%. In case of zirconiumoxid it is possible to add up to about 10% without producing adeleterious effect upon the me- 'chanical qualities of the resultantfilament or the life of the lamp made up with such filaments. When amixture of thorium and zirconium oxid is employed it is possible toincrease the amount of the addition up to 15%. While these maximumpercentages are satisfactory in some cases it is, of course, preferable,as stated above, that the quantities added be dfiisiderably smaller.

I have observed that when raw filaments are squirted from a paste madeup in conformity with the rocedure outlined above and are then sub ectedto the customary process of forming the tungsten filament,

that is, heating it to a high temperature in a reducing atmosphere,there appears to be a partial, if not complete, reduction of theauxiliary metallic oxygen compounds in the raw filament. It is believedthat during this forming process such oxids are reduced to sub-oxidswhich latter give to the filament the required qualities and moreoverare conductors of the first class. This is indicated by the fact thatthe resistance of such filaments and their temperature coefficients aredistinctly altered.

The appearance of a filament containing offset-resisting additions isclosely similar to the appearance of a filament composed of tungstenonly. During the burning of lamps provided with my filaments, however,the delay of the time when the crystallization of the filament becomesharmful can be distinctly observed.

It will, of course, be understood that my invention is not limited inits application to use in connection with any particular process ofproducing the filaments, but that, if desired, it may be employed inconnection with any other process than that specifically set forth. Itis also to be understood that my invention is not alone applicable totungsten filaments but that it is also applicable to all filamentssuitable for incandescent lamps and subject to offsetting or faulting inuse.

In the subjoined claims, the expression refractory metal of the tungstentype is to be understood as comprising all metals which can besubstituted for tungsten in the manufacture of incandescent electriclamp filaments.

I am aware that it has been proposed to make lamp filaments consistingof a mixture of a metal and an oxid, but, in such cases, the oxid formsa large part of the finished filament, whereas, in my process, the oxidor other metallic compound is added only in sufiicient quantity toaccomplish the desired result. This result is essentially the preventionof harmful internal alteration or offsetting, and the fact that theaddition of other substances than the filament metal will produce thisresult has never, so far as I- am aware, been suggested prior to mypresent invention.

I claim as my invention:

1. A filament composed mainly of a metal that tends to offset, whenutilized as a conductor of electricity, and containing an offsetresisting material.

2. An essentially metallic filament for incandescent electric lampswhich consists mainly of a metal that tends to offset, but which resistsoffsetting.

3. A filament for incandescent electric lamps which consists mainly oftungsten and which resists offsetting.

4. A filament for incandescent electric lamps consisting mainly of amaterial that tends to develop structural alterations when utilized as aconductor of electricity and 7. A filament composed mainly of a metalthat tends to ofi'set when utilized as a c0nductor of electricity andcontaining a plurality of offset-resisting materials.

8. A filament composed mainly of a metal that tends to offset, whenutilized as a conductor of electricity, and containing thoria andanother offset-resisting material.

9. A filament for incandescent electric lamps composed of an intimatemixture of a refractory metal of the tungsten group and an additionalmaterial which comprises at least one of a group of substances includingthorium, zirconium, erbium, cerium, and lanthanum, and the oxygencompounds of the said metals, the said additional material being presentin substantially sufficient quantity to prevent deleterious alterationwithin the said filament during use.

10. The process of making essentially metallic filaments forincandescent electric lamps comprising the steps of adding to thematerial composing such filaments an offsetresisting material 1n onlysubstantially sufii-- cient quantity to resist deleterious alterationwithin the said filaments during their use, and thereafter shaping themixture into filamentary form with application of heat.

11. The process of making tungsten fila ments for incandescent electriclamps comprising the steps of adding thoria to the tungsten insufficient quantity to resist deleterious structural alteration of suchfilaments during their use, and thereafter shaping the mixture intofilamentary form with application of heat.

12. The process of making essentially metallic filaments forincandescent lamps comprising the steps of adding to the materialcomposing such filaments a plurality of offset-resisting substances andthereafter shaping the mixture into filamentary form with application ofheat.

13. The process of manufacturing filaments for incandescent lamps whichconsists in making a plastic paste composed of a refractory metal of thetungsten group, an oxygen compound of metal of the rare earth groupwhich is a conductor of the second class and. a suitable agglutinant,forming such paste into filaments and subjecting the same to a hightemperature in a suitable atmosphere, thereby transforming saidconductor of the second class into a conductor of the first class.

14. A filament for incandescent electric lamps, consisting of anintimate mixture of a refractory metal of the tungsten group and anotherconductor of the first class, which other conductor consists of a metalof a rare earth and the suboxid thereof, and

has been transformed during the manufacture of the filament from aconductor of the second class into one of the first class.

15. A filament for incandescent electric lamps consisting of an intimatemixture of a refractory metal of the tungsten group with a compound of ametal of the rare earth group, which compound is a conductor of thefirst class.

16. A filament for incandescent electric lamps, consisting of anintimate mixture of a refractory metal of the tungsten group and lessthan of another conductor of the first class which comprises a mixtureof at least one metal 'of the rare earth group and the suboxid thereof.

In testimony whereof, I have hereunto subscribed my name this 28th dayof N ovember, 1906.

ANTON LEDERER. Witnesses:

ALvEs'ro S. Hooun, AUGUST Fuocnn.

